Single and twin coincidence points for multivalued maps in Fréchet spaces (Q1975317)

The authors obtain several results on the existence of one or two coincidence points for set-valued maps between Fréchet spaces where one of the maps has closed graph and the other one is a so-called DKT map. (A map \(F\) from a Hausdorff topological linear space \(Z\) to the nonempty subsets of a convex set \(W\) of a Hausdorff topological vector space \(X\) is said to be a DKT map if there is an upper semicontinuous map \(B\) from \(Z\) into the nonempty subsets of \(W\) such that \(\text{conv}B(x)\subset F(x)\) for all \(x\in Z\).) \{On p. 91, ``Hausdorff topological space'' has to be replaced by ``Hausdorff topological vector space'' throughout.\}.